Aldabra Giant Tortoise

The Aldabra giant tortoise is one of the largest and longest-lived land tortoises. It is the last extant species of a group of giant tortoises, known for its thick, domed shell and ability to live 150 years. Native to the Aldabra Atoll in the Seychelles, the Aldabra giant tortoise inhabited the islands of the Western Indian Ocean.

Introduction To Aldabra Giant Tortoise

The Aldabra Atoll is a part of the Seychelles in die Indian Ocean, and the Aldabra Giant Tortoise is a large reptile found on the Aldabra Atoll in Seychelles. So its name derives from its habitat. An atoll is a ring-shaped coral reef, island, or series of islets. The habitat inside the atoll, protected from the open sea by the sturdy reef, is called a lagoon. Sometimes, atolls and lagoons protect a central island. The tortoise can grow to be over 4 feet long and weigh up to 250 kilograms. The Aldabra Giant Tortoise has a massive defensive shell known as a carapace that protects the vulnerable, soft body within. These animals are terrestrial and inhabit a wide range of habitats, including mangrove swamps, scrub forests, and coastal beaches and dunes. The Aldabra Giant Tortoise mainly dwells in the grassy and swampy regions of the Aldabra Atoll. They are found both individually and in herds, which tend to gather mostly on open grasslands. The tortoise is unique because it is the only extant species in its genus, Aldabrachelys.

Common Name

Aldabra tortoise, Giant tortoise

Scientific Name

Aldabrachelys gigantea

Size

3-4 feet

Weight

159-250 kg

Average Life Span

100-150 years

Found In

Group(s)

Scientific Name Of Aldabra Giant Tortoise

The Aldabra giant tortoise is a species of tortoise in the family Testudinidae and the genus Aldabrachelys. The species is endemic to the Seychelles, with the nominate subspecies, A. g. gigantea, native to Aldabra Atoll. It is one of the largest tortoises in the world. The scientific name for the Aldabra Giant Tortoise is "Aldabrachelys gigantea". They are native to the Aldabra Island, one of the Seychelles, northeast of Madagascar in the Indian Ocean.

Facts And Features About Aldabra Giant Tortoise

The Aldabra giant tortoise is one of the most interesting creatures on Earth. Here are some incredible facts and features about this amazing creature:

  1. The Aldabra giant tortoises can weigh up to 250 kg and live for over 150 years. They have a massive defensive shell known as a carapace that protects the vulnerable, soft body within.
  2. Their shells are typically beautiful, brown or black, with dark spots for males, while females are lighter in colour. Their skin is also very colourful with shades of yellow, green and blue being common.
  3. These giant tortoises also have long necks and legs, which makes them very graceful animals. 
  4. Another interesting fact about Aldabra giant tortoises is that they can swim and hold their breath underwater for up to 30 minutes, which means they can travel between islands if they need to.
  5. They also have very strong jaws, which they use to crush hard nuts and other food items.
  6. The Aldabra giant tortoises are the only species of tortoise that can exist completely underwater for up to 5 minutes. They have a small hole on the top of their head called a fontanelle that allows them to breathe when their head is underwater. 
  7. They are also one of the most sexually dimorphic of all vertebrates, with males being around twice as large as females. Females lay clutches of eggs weighing between 40 to 75 grams, which they incubate for up to 8 months.
  8. Aldabra giant tortoises consume so much vegetation that they can change the appearance of an island over time by removing large amounts of foliage.
  9. Their favourite prey items include prickly pear cactus, hibiscus flowers and coconuts. They can go without food or water for long periods.
  10. Tortoises are considered reptiles and not amphibians because they are vertebrates, that is, they have a backbone. Their head and legs are covered in scales, and they breathe through their lungs.

Appearance And Anatomy Of Aldabra Giant Tortoise

Aldabra giant tortoise is a species of large, herbivorous tortoise endemic to the Aldabra Atoll in Seychelles. It is the largest living species of tortoise and the second-largest reptile in the world, after the Galapagos giant tortoise. The head is relatively small and blunt, with a wide mouth that opens into a long neck. Their shells are light brown or tan with dark blotches, and their skin is pale yellow. These tortoises' eyes and nostrils are located on the top of their heads. They have powerful, thick legs like an elephant and webbed feet. Aldabra giant tortoises have strong jaws and small air chambers inside their shells that help hold up their massive bodies. The carapace is high and convex, with prominent ridges on each scute. Their plastron is small and flat, with two hinges that allow the animal to close its shell completely. The males have a concave plastron (belly shell) that aids in mating.

An adult Aldabra giant tortoise can weigh between 159 to 250 kg and measure between 3 to 4 feet long. Female Aldabra giant tortoises are typically smaller than the male Aldabra giant tortoise. The male's carapace length can measure 4 feet, and they can weigh up to 250 kg, while the female's carapace can measure 3 feet and can weigh 159 kg.

Aldabra giant tortoise's eyes and nostrils are located on the top of their heads, so they can breathe and see while they’re submerged in water. They have powerful legs and webbed feet, which help them move through the water quickly. Aldabra giant tortoises use their strong jaws to crush hard fruits and vegetables. They have large, dome-shaped shells to protect the delicate bodies that lie beneath their shells. Male Aldabra giant tortoises are considerably larger than female Aldabra giant tortoises and have longer, thicker tails. 

Habitat And Distribution Of Aldabra Giant Tortoise

Aldabra giant tortoise is the world's largest living tortoise and the second-largest species of tortoise after the Galapagos giant tortoise. These tortoises enjoy a variety of habitats like coastal beaches, coastal dunes, grasslands, mangrove swamps, and scrub forests. There are two main types of tortoise:

  1. Domed tortoises, which live in the cooler regions of the archipelago and
  2. Saddle-backed tortoises, which live in dry, coastal environments

The Aldabra giant tortoise is distributed across three islands in Seychelles, Grand Terre, Picard Island and Denis Island. They are found on Aldabra Island, one of the Seychelles, northeast of Madagascar in the Indian Ocean. Aldabra Islands, an atoll, one of the world's largest, in the Indian Ocean about 600 miles (1,000 km) southwest of the Seychelles group and part of the Republic of Seychelles. They were introduced to Mauritius and the Reunion Islands. Aldabra Island is a coral atoll (An atoll surrounds a body of water called a lagoon) bordered by jagged limestone and small beaches and encloses a large mangrove-bordered lagoon.

Common Types Or Subspecies, Characteristics And Examples Of Habitats

The Aldabra giant tortoise (Aldabrachelys gigantea) has four recognised subspecies, and the most prominent subspecies is the Aldabra tortoise (Aldabrachelys gigantea gigantea). The four subspecies of Aldabra giant tortoises are,

  1. Aldabra tortoise (Aldabrachelys gigantea gigantea)
  2. Arnold's giant tortoise (Aldabrachelys gigantea arnoldi)
  3. Seychelles giant tortoise (Aldabrachelys gigantea hololissa) and
  4. Daudin's giant tortoise (Aldabrachelys gigantea daudinii)

The first three are extant, while Daudin's giant tortoise is extinct.

The Aldabra tortoise (Aldabrachelys gigantea gigantea) is the most well-known and common subspecies of the Aldabra giant tortoise (Aldabrachelys gigantea). The main population of the Aldabra giant tortoise resides on the islands of the Aldabra Atoll in Seychelles. The atoll has been protected from human influence and is home to some 100,000 giant tortoises, the world's largest population of animals.

The Arnold's giant tortoise (Aldabrachelys gigantea arnoldi), also known as the Seychelles saddle-backed giant tortoise. This subspecies is an inhabitant of the Seychelles and is characterised by its saddle-backed shell or carapace.

The Seychelles giant tortoise (Aldabrachelys gigantea hololissa) is also known as the domed Seychelles giant tortoise. This subspecies is native to the Seychelles and is characterised by its more domed shell.

The Daudin's giant tortoise (Aldabrachelys gigantea daudinii) is an extinct subspecies, but its historical existence is recognised and was also found in the Seychelles.

Aldabra giant tortoises are characterised by a massive defensive shell known as a carapace that protects the vulnerable, soft body within. Their carapace (upper shell) has a small neck plate that is usually visible, a feature absent in other species of giant tortoises. The males have a concave plastron (belly shell) that aids in mating. Aldabra giant tortoises are brown to dark grey or black with a highly domed, thick carapace. They have long necks, relatively small, blunt, scally head with a wide mouth. Their back legs are thick and somewhat resemble the legs of an elephant. The front legs, on the other hand, are rather flat and covered with large scales. Their toes have no webbing between them, and many species have five claws on each front foot. The male Aldabra giant tortoise, one of the largest land tortoises. They can weigh between 159 to 250 kg and reach a length of 3 to 4 feet. Males are typically larger than females. The largest recorded free-roaming Aldabra giant tortoise weighed 305 kg, while some male Aldabra giant tortoises reached lengths of up to 4.25 feet. Aldabra giant tortoises are known for their impressive longevity, with a typical lifespan between 100 to 150 years or more.

Aldabra Island, which is a group of islands in the Indian Ocean, is the common habitat of the Aldabra Giant Tortoise. It is a marine habitat that ranges from coral reefs to seagrass beds and mangrove mudflats with minimal human impact. The property is an outstanding example of an oceanic island ecosystem in which evolutionary processes are active within a rich biota.

Diet And Prey Of Aldabra Giant Tortoise

The Aldabra giant tortoises are primarily herbivores that feed mainly on leaves, grasses, flowers, fruits and cacti. They have also been known to eat invertebrates, such as insects, snails, worms, crabs and lizards, but this does not make up the majority of their diet. They will eat meat when it is available and possibly even eat the carcasses of dead tortoises. So, while they are largely herbivorous, they can be considered opportunistic omnivores due to their occasional meat consumption.

Aldabra giant tortoises typically have a slow metabolism, so they can digest tough woody plants easily. Their strong jaws also help them to crush through the hard shells of fruits. They are grazers and browsers, and consume so much vegetation that they can change the appearance of an island over time by removing large amounts of foliage. Some of their favourite prey items include prickly pear cactus, hibiscus flowers and coconuts. Aldabra giant tortoise can go without food or water for long periods.

Behaviour And Lifestyle Of Aldabra Giant Tortoise

The giant tortoises are generally shy animals, but they can be very aggressive when threatened. They can defend themselves by using their powerful jaws and sharp claws. While they are characteristically slow and cautious, they are capable of appreciable speed. Aldabra giant tortoises are also known to attempt perilous acrobatic feats, rising precariously on their hind legs to reach low branches. They have also been known to ram intruders with their shells. Aldabra giant tortoises are diurnal animals, spending most of their daytime foraging for food, resting in the shade or swimming in the ocean when not grazing.

Aldabra giant tortoises live in social groups, often from small herds of 5 to 10 animals, with males occupying territories that overlap those of several females. They are most active in the mornings when they spend time browsing for food. Aldabra Giant Tortoises dig underground burrows or rest in swamps to keep cool during the heat of the day. They can survive for long periods without food or water. Aldabra Giant Tortoises can go without eating for up to a year and can survive for up to two weeks without water. These animals can be very aggressive towards members of their species, biting and roaming at each other in territorial disputes. They risk death by tipping onto their backs and being unable to right themselves. This unusual behaviour led Mexican biologist José Antonio de Alzate y Ramírez to refer to the Aldabra as the "ninjas" of the tortoise world.

Reproduction, Babies And Lifecycles Of Aldabra Giant Tortoise

The tortoise is a critically endangered species with a unique life cycle. Aldabra Giant tortoises reproduce slowly, making their populations particularly vulnerable to extinction. Males and females mate during the breeding season, which usually occurs from February to May. The males have a concave plastron (belly shell) that aids in mating. Female Aldabra giant tortoises lay clutches of eggs once every 2 to 4 years, which are roughly the size of tennis balls and weigh between 40 to 75 grams. The eggs are laid in shallow, dry, flask-shaped nests and take 4 to 8 months to hatch, depending on the temperature. Warmer temperatures can lead to hatching in around 4 months, while cooler temperatures can take over 8 months.

When young tortoises do hatch, they need to dig themselves out of the nest. They hatch from their eggs fully independent. The baby tortoises are just around 2.5 to 3 inches long and weigh less than 15 to 113 grams. Baby tortoises spend the first few years of their lives eating leaves and grasses. They grow slowly until they reach sexual maturity at around 25 years old, depending on size rather than age. At that point, they start looking for a mate and can live for another 100 years. The lifespan of an Aldabra giant tortoise ranges from 100 to 150 years. However, it can extend up to 170 or over 200 years.

Predators And Threats Of Aldabra Giant Tortoise

Aldabra giant tortoises have no significant natural predators except for humans. However, their eggs and young tortoises have been preyed upon by various animals like birds of prey, sharks and giant crabs. Additionally, their eggs and young have also been preyed upon by monitor lizards and snakes. Some introduced species like dogs, cats, feral pigs and rats have preyed on their eggs and hatchlings. Other introduced herbivores, like goat, can compete with tortoises for food and resources.

Aldabra giant tortoises are also threatened by habitat loss, degradation, climate change and poaching. Humans have historically hunted these tortoises for food and their shells. On the other hand, rising sea levels due to climate change threaten the Aldabra atoll, which is only a few meters above sea level. This can lead to habitat loss and increased salinity, affecting vegetation and water sources. Their natural habitat is also being destroyed by human development, which is causing them to lose their traditional nesting grounds and food sources.

Population Of Aldabra Giant Tortoise

The Aldabra giant tortoise is the largest extant tortoise in the world and one of the oldest living reptiles. These gentle giants are found only on the Aldabra Atoll in the Seychelles, a group of islands in the Indian Ocean, which has been protected as a UNESCO World Heritage site. The Aldabra giant tortoise (Aldabrachelys gigantea, also known as Geochelone gigantea) has received modest protection. As a result, it has attained a total population of more than 100,000, according to some estimates, with densities in some areas ranging from 30 to 160 individuals per hectare. There are approximately 150,000 Aldabra Giant Tortoises left in the world. Aldabra giant tortoises are endemic and critically endangered due to habitat loss, degradation, climate change, introduced predators (feral pigs, rats, dogs, cats, etc) and poaching for food and trade.

Importance Of Aldabra Giant Tortoise

The Aldabra giant tortoise plays an important role in the ecosystem.

  1. Aldabra giant tortoise alters the habitat when it's vigorous searches for food, fells trees, and creates new pathways called "tortoise turf", which is a mosaic of grasses and herbs and clearings that are beneficial for other animals.
  2. It also plays an important role in the dispersal of seeds. The giant tortoises can modify the vegetation structure, and by grazing on dry vegetation, they reduce the amount of flammable material, helping to prevent the spread of wildfires.
  3. Aldabra giant tortoise also creates habitat heterogeneity, and can even structure the population biology or the trait evolution of plant species.
  4. These tortoises provide important habitat spaces for smaller animals and insects within their burrows.
  5. As the largest animal in its environment, the Aldabra tortoise performs a similar role to the one occupied by elephants in Africa and Asia.
  6. These majestic creatures have long been revered by local communities and are deeply entrenched in folklore and traditional practices.
  7. The Giant tortoises of the Indian Ocean islands were an important source of food for sailors. These animals were once heavily hunted for their meat and shells, which were used to make souvenirs and jewellery, but now they are mainly used as tourist attractions.

In The Zoo

The Aldabra Giant Tortoise is a majestic creature that can be found in the zoo. These gentle giants are considered one of the largest tortoises in the world, with some individuals weighing over 226 kg. 

Aldabra Giant Tortoises have a lifespan of up to 150 years, making them one of the longest-living animals on Earth. In captivity, they require plenty of space to roam and graze as they are herbivores. Zoos provide them with ample opportunities for exercise and ensure their diets consist of nutritious greens such as leafy vegetables, dark lettuce, and hay.

Visitors to zoos can observe these fascinating creatures up close and learn about their unique behaviours from dedicated zookeepers who care for them daily. One particular zoo that boasts an impressive collection of Aldabra giant tortoises is the Virginia Zoo, the Africa Okavango Delta Trail. Another zoo that houses these amazing animals is Taronga Zoo in Sydney, Australia.

Classification And Evolution Of Aldabra Giant Tortoise

The classification of the Aldabra giant tortoise (Aldabrachelys gigantea) is a subject that continues to fascinate researchers and wildlife enthusiasts alike. This species belongs to the Testudinidae family and the genus Aldabrachelys, is one of the largest living tortoises, recognised by its distinct shell pattern and large size. These tortoises are believed to share a common ancestor with their closest relatives, the Galapagos giant tortoises, dating back approximately 25 to 30 million years, although they evolved independently and adapted to the unique environment of the Aldabra Atoll in the Seychelles. One of the most distinctive features of the Aldabra giant tortoise is its long neck and large, domed shell, which protects predators.

In terms of evolution, the Aldabra giant tortoise's evolutionary history is linked to Madagascar. They evolved from ancestors of Aldabrachelys abrupta, a giant tortoise species that lived in Madagascar for 15 million years and migrated to the Seychelles. These incredible creatures have adapted to their environment on the remote Aldabra Atoll in the Indian Ocean. With limited resources and isolation from other species, they have evolved unique traits that enable them to survive in this harsh habitat. The classification of the Aldabra giant tortoise has undergone several changes over time, thanks to advancements in genetic research, which have helped scientists better understand its evolutionary history.

Relationship With Humans

The relationship between Aldabra giant tortoises and humans has been long and varied. These tortoises were first discovered on the Aldabra Atoll by Portuguese sailors in 1505. The sailors killed hundreds of tortoises for food, oil and ship-building materials. In 1771, when French explorer Louis de Freycinet visited the Atoll, he found only 4 living tortoises.

Their relationship with humans has been complex and largely negative historically, marked by exploitation for food and habitat destruction. Human activities, including agriculture and development, have degraded their natural habitat. These animals were once heavily hunted for their meat, fat and shells, which were used to make souvenirs and jewellery, but now they are mainly used as tourist attractions.

Today, they are protected by law, and their numbers have rebounded somewhat, but they remain vulnerable to invasive species and habitat loss due to climate change. The Seychelles government has even created a national park to protect these animals. Now, they are a popular attraction in zoos and wildlife parks. The Aldabra giant tortoises are iconic symbols of the Seychelles. They were used as transportation by sailors in the Indian Ocean and later became popular as pets. Today, they are still kept as pets by wealthy people all over the world.

Conservation Status Of Aldabra Giant Tortoise

The Aldabra giant tortoise population is estimated to be 100,000 to 150,000 individuals. The giant tortoise is listed as "vulnerable" to extinction on the IUCN Red List. They are threatened by habitat loss, poaching, climate change and invasive species. Despite their conservation status, the tortoises are still found in the wild today. They can be found on the islands of Aldabra, Assumption, cosmoledo and Farquhar in the Seychelles.

Despite its "vulnerable" status, the tortoise is doing relatively well today. Thanks to effective conservation measures, the population has increased somewhat in recent years. Additionally, there are now several thousand captive individuals in zoos and private collections around the world. This gives hope that this magnificent creature may one day be saved from extinction.

Difference Between Aldabra Giant Tortoise And Galapagos Tortoise

Aldabra Giant Tortoises and Galapagos Tortoises are both among the largest tortoises in the world, but they have distinct differences.

  1. Aldabra Giant Tortoises have smaller, narrower, rounded heads and pointy noses. On the other hand, Galapagos Tortoises have very broad, blunt heads and stumpy noses.
  2. The carapace of Aldabra Giant Tortoises has a small scute above the neck called the nuchal scute, while the carapace of Galapagos Tortoises lacks a nuchal scute.
  3. Male Aldabra Giant Tortoises can grow up to 4 feet long and weigh up to 250 kg, while male Galapagos Tortoises can grow up to 6 feet long and weigh up to 417 kg.
  4. Aldabra Giant Tortoises are known to be more personable and may approach humans for food or scratches, while Galapagos Tortoises are more skittish.
  5. Aldabra Giant Tortoises are found in the Indian Ocean, specifically Aldabra Atoll in the Seychelles. Conversely, Galapagos Tortoises are native to the Galapagos Islands.
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram